72cc Stock Setup Concerns

[1man8scoots]

7.5s with a cast kit is a bad idea. Too much lugging of the engine and Temps will spike. Just imagine it being like going up a hill all the time.

[Rancher1]

The three of us seem to have very similar setups and getting challenged with high temps. My top speed was 54mph (untucked) and was thinking it should be closer to 60, but perhaps that's a bit unrealistic. It sounds like mid 50s is what our setups can do. Scott what temps are you seeing?

It's possible I have an air leak. Going to check when I get everything back together including spraying some copper seal per forum suggestion. I also have a #100 and #105 main jet coming in (thanks Limp) that I want to experiment with it to see if I can actually foul my plug and keep temps lower. I'll let you guys know what I find in probably a week. I run a #96 and the plug doesn't look wet. Ran a #88 and the temps rose faster. If I hold WOT for a little bit, it'll climb to 370F then I back off, blipping throttle on decel but it'll still spike to 380F. I haven't pushed WOT that hard as I'm a bit hesitant to drive it over 380F with likely 390-400F spikes on decel while this bore is still breaking in. Maybe we'll see improved temps after break-in?

I'm also going to play around with the air scoop Graphite now sells. I'm a little concerned it might hit the skirt when my 190 lbs * hits a pothole. Well mess around with it and keep you guys posted, especially if it helps with temp. If you guys figure out how to manage sustained WOT under 370F that would be awesome. Maybe I'll switch to Castor 927 at a higher premix like 25:1 with a monster jet and see what happens.

[1man8scoots]

Too much oil with these tiny engines and you will get a clogged exhaust port or exhaust over time. There's an air leak. My tmps never hit over 370 and once it hit 380 with a 82 jet. I'm running a 90 now and it's too fat still but I'm not dropping the bowl Again.

[Dbroogs]

I am seeing lower temps after break-in. Took the motor apart after around 100 miles. Now have around 400 miles on the motor. Temps continually dropped to about 350 miles to where now 370 is my max spike with the half throttle problem I have. I think the new bores overheat easy but I also had an air leak somewhere. Max temps dropped around 10, maybe 15, degrees total from 100 miles to 350 miles.

Basically if you are above 380 and it will keep rising then strip it down and put it back together meticulously. If you are under 380 then after break in there will be a bit less friction and temps will probably drop a bit. Does this sound correct to you scooter legends?

[scottinscotty]

I don't use a CHT gauge, I just Read the Plug... never had any issues but you've got me curious.. I may have to invest in a CHT gauge, on the other hand I feel like it may have me worring about excessive temps.. Also, I use the Stock Oil pump.. just Zip Tied wide open. One day with my old build I rode over close to 90 miles with 0 issues.. I don't like the premix option.. and never will change to premix..

[Dbroogs]

Well i rode it around today and I still have an air leak, but a small manageable one. I went wot for 4 miles and the temps were fine 370 max. But I know i have an air leak because if it hits 370, under half throttle after long wot or wot up a hill for a long time, then they climb and reach 380 and max at 390. So this sounds like a small air leak opening up at those high temps. I think i am going to throw in a 94 after I look at the plug. If it isn't too rich i will put it in. Also there seems to be less smoke so maybe richer is the way to go.

Edit: Plug looked decent but not too rich. No excess oil either. Like i said i think i have a micro leak that expands when temps go above 370ish so looks like I will try and keep that as my max. Rancher, how would one go about spraying the copper spray on the gaskets, just curious? I might tear it down and redo everything again. I thought i would hate having to redo everything but it is kinda fun tearing into it over and over.

[Rancher1]

I haven't used sealants in a long time and normally don't use them in general unless I need a quick fix on an otherwise tough fix. But, if I have a suspect leak, might as well try a spray which is easy to use. I've just used spray like spray paint on both sides of the gasket. This is what I do but others may gave better methods:

- Clean the manifold surfaces so it's free of old gasket material. Use alcohol or whatever solvent to wipe down and degrease manifold surfaces.
- I softly wash with soap/water and degrease the new gasket itself. Ensure gasket and manifold surfaces are dry before proceeding. I like to accelerate drying with compressor.
- Put gasket on a wire hanger and spray both sides. Let it sit for a bit till it's tacky.
- Install tacky and let sit for another while before starting her up.

That's just what I do though - pretty straight forward. You can also precoat the manifold surfaces, but that's kinda tricky for our usage and would probably make it too thick and ooze out too much. My spray is arriving this weekend. I'll take some pictures if you'd like.

http://www.amazon.com/dp/B000HBNUDQ/ref ... pper+spray

[1man8scoots]

You can get the copper coat spray from an oreily auto parts or most other chain stores

[scottinscotty]

When I installed my Cylinder Kit I make sure the Matting Surfaces are Spotless, Cleaning the old Gasket Residue with a Razor Blade & Shop Vac (to Clean and Debris that May Fall in the Case), The Reed Block is Another Very Important Surface to Make Sure it's Spotless as Well (If you Installed the Malossi Reeds), Not Sure I've ever had a Air Leak Issue..

[scottinscotty]

I think the Temp Issues are Related to the Stock Carb, .. WOT give the Cylinder the Fuel It Needs to Cool Down, Where as with an Aftermarket Carb you can Up the Pilot Jet and Really Dial In the Fuel Intake.

[Rancher1]

Yes, I'm fairly sure the high temps at partial throttle, especially deceleration, is because the pilot in the stock carbs are too small for our bigger bore, better breathing setups. I don't see much we can do about that other than (attempting to) drilling out the pilot or swapping to a larger carb with replaceable pilot. That's why it's especially important to try keep WOT temps down so the decel spike isn't too extreme. This is the first time I'm running a BBK with the stock carb so some of these carb tuning/breakin temps are new to me. I'd really like to keep the stock carb only to keep the noise down with airbox. Hmm, maybe I should design an airbox for bigger carbs and 3D print it. Nylon stock (fuel resistant) can be a little pricey given the size we're talking about.

I installed an air scoop and a cooler plug but haven't had the chance to run the bike yet, except for a few heat cycles on the stand.

[Rip_City_Spree]

Get a better carb in the long run its so worth it. why spend the money on the bbk then be constantly worrying wether or not it's gonna get to hot. Put a better carb on there it makes tuning so much easier. And piece of mind is a bonus. Been running my 24mm polini carb and love it. That was one of the first things I did. I tried to drill jets on my stock carb and realized that it's so much better to be able to change the jets rather than guessing on the size of what ever I drilled out.

[Rancher1]

I totally agree with you, however I really need to keep the noise down on this bike and the stock carb with airbox keeps it pretty silent. Maybe this just means I need a second bike.

I had a Spree with BBK but it just didn't have the guts to make it up my hills, so sold it. I'm considering looking for a stock un-titled/parts SA50 bike. What's a fair price for something like that? I've seen similar bikes sold for ~$300-$400. Then I could make my existing bike a real street rider.

[Rip_City_Spree]

The first bbk I put on my elite was a contessa with polini carb pod filter and R1 exhaust was a sleeper. Was a rocket light to light and very quiet. A little louder than stock but not loud enough to * off the neighborhood at 5:30 in the morning. just saying because you want to keep the noise down doesn't mean you have to have a slow scoot

[1man8scoots]

I feel my girl friends malossi cast iron with stock carb and malossi wild lion exhaust is fairly quick. Great low end. As far as the pilot being non changeable, there's a screw for that. Ped runs a stock carb and a corsa.
Her kit now has 410 miles on it and going stronger than I'd have guessed. Never hit 400 and stays around 350-370. Just be sure no air leaks.